The present invention relates to code division multiple access (CDMA) signal analysis, and more particularly to a display of code power levels and relationships of multiple spreading factor orthogonal codes in a CDMA signal.
In a CDMA signal using orthogonal codes, all of which are the same length (also known as spreading factor), the amount of power present in each code, i.e., code domain power (CDP), may be displayed by plotting the power in each code versus the code number index on a two-dimensional graph. This is a conventional and well-understood manner using linear index code order for displaying CDP information. Newer CDMA systems, such as cdma2000, now specify use of codes of varying spreading factors, i.e., of different lengths, which complicates the display of CDP. Specifically codes of smaller spreading factor when displayed in a CDP graph appropriate for the largest spreading factor code appear dispersed into multiple sub-codes at fixed distances determined by their relationship to the larger spreading factor code system, i.e., a code with a spreading factor of 16 when displayed on the code graph for a spreading factor of 128 has 8 sub-codes spaced 8 indices apart. Also the total code power of the lower spreading factor code is not correctly indicated by the power levels of the individual sub-codes. Both of these factors cause difficulty in interpreting the results of CDP calculations when codes of different spreading factor values are present.
U.S. Pat. No. 6,219,340 describes one method of displaying power levels for a CDMA signal having orthogonal codes with different spreading factors or code layers. In this display a power level for each active code channel is displayed using a vertical bar, with the width of the bar indicating in which code layer each active code channel is active. However this display does not highlight the relationship of sub-codes to the base code.
What is desired is a display of code power levels and relationships of multiple spreading factor orthogonal codes in a CDMA signal that highlights the relationship of sub-codes to the base code and indicates the total power of the base code.